The invention relates to a camshaft for an internal combustion engine, in particular a motor vehicle.
Such a camshaft for an internal combustion engine, in particular a motor vehicle, is already known from DE 10 2009 022 657 A1, for example. The camshaft comprises a fundamental shaft which has a first toothing in the form of an external toothing. Furthermore, the camshaft comprises at least one cam element which is arranged on the fundamental shaft and has a second toothing formed as internal toothing. The cam element can be displaced in the axial direction relative to the fundamental shaft and is connected to the fundamental shaft in a rotationally fixed manner via the gear teeth so that, for example, torques can be transmitted between the cam element and the fundamental shaft via the gear teeth. The fundamental shaft, for example, is a drive shaft from which the cam element, which functions as an output shaft, can be driven. In particular, the cam element is used to actuate at least one gas exchange valve of the internal combustion engine, in particular to open it.
In addition, EP 0 606 820 B1 reveals a tension anchorage for at least one tension element running inside a cooling tube, with an anchor plate supported on a building component.
From the WO 2010 12 371 A1 a toothed shaft connection between a hollow shaft or hub provided with an internal toothing and a shaft provided with an external toothing is known. In order to achieve radial backlash compensation in the splined shaft connection or to enable radial bearing and centering of the hollow shaft or hub on the shaft, it is suggested there that the two toothings lie opposite each other over a part of their length in the region of a tip diameter and/or a root diameter of the external toothing with clearance fit and lie opposite to each other in the region of adjacent tooth flanks of the internal and external toothing at a greater distance, and in that the two toothings lie opposite to one another over another part of their length in the region of the adjacent tooth flanks of the internal and external toothing with clearance fit, while in the region of the tip circle diameter and the root circle diameter they lie opposite one another of the external toothing with radial clearance. The tooth shaft connection is preferably arranged between a camshaft and cam carriers of a valve train for gas exchange valves of an internal combustion engine which can be displaced on the camshaft.
From DE 10 2008 064 340 A1 a valve train for gas exchange valves of an internal combustion engine is known, with a basic camshaft and several axially displaceable and radially guided cam carriers on the basic camshaft, wherein the base camshaft has for each cam carrier at least one external toothing portion and each cam carrier at least one internal toothing portion meshing with the external toothing portion of the base camshaft, and wherein the base camshaft has cylindrical shaft portions between adjacent external toothing portions. To facilitate the manufacture of the ground camshaft, it is suggested that each cam carrier be radially guided on at least one of the cylindrical shaft sections.
The object of this invention is to further develop a camshaft of the type mentioned above in such a way that a particularly advantageous noise behavior can be achieved.
In order to further develop a camshaft of this type in such a way that a particularly advantageous noise behavior can be achieved, it is provided in accordance with the invention that at least one of the toothings has teeth whose respective tooth width, running in particular in the circumferential direction of the fundamental wave, varies in the axial direction of the fundamental wave. This can at least limit the backlash between the toothings in at least one position of the cam element relative to the fundamental shaft, therefore significantly reducing the generation of unwanted tooth noise compared to conventional camshafts. At the same time, sufficient mobility of the toothing and therefore of the cam element relative to the fundamental shaft can be achieved so that the cam element can be shifted axially relative to the fundamental shaft.
The invention is based in particular on the knowledge that this displacement of the cam element relative to the fundamental shaft usually requires a minimum clearance, which is usually ensured by a toothing clearance between the toothings. In addition, tolerances, i.e., so-called manufacturing tolerances, occur due to the manufacturing process, which further increase the backlash. It was found that the backlash is exponentially integrated into the acoustic behavior of the camshaft, so that undesirable impulse noises can occur if the backlash is undesirable. Such unwanted impulsive noises can now be avoided with the invented camshaft, since the backlash, especially in at least one position of the cam element relative to the fundamental shaft, can be kept particularly low while at the same time realizing the displaceability of the cam element relative to the fundamental shaft.
For example, the cam element can be moved between at least two positions relative to the fundamental shaft and can therefore be moved in the axial direction of the fundamental shaft relative to it in a translatory manner. These positions are preferably end settings or end positions, wherein the cam element can be moved axially to the respective end position relative to the fundamental shaft, but not beyond it. Due to the varying tooth width, it is possible, at least in the end settings, to keep the backlash particularly low and at the same time to ensure the displaceability of the cam element relative to the fundamental shaft, so that a particularly advantageous function and noise behavior of the camshaft can be achieved.
Further advantages, features and details of the invention result from the following description of a preferred design example as well as from the drawings. The features and combinations of features mentioned above in the description as well as the features and combinations of features mentioned below in the description of the figures and/or shown to the figures alone can be used not only in the combination indicated in each case, but also in other combinations or in a unique position without leaving the scope of the invention.